Involvement of cellular double-stranded DNA break binding proteins in processing of the recombinant adeno-associated virus genome

Unlike postmitotic tissues in vivo, transduction of cultured cells is poor with recombinant adeno-associated virus (rAAV). The ability of rAAV to tran sduce cells is greatly enhanced by a variety of agents that induce DNA dama ge and is elevated in cells defective in the ataxia telangiectasia gene pro duct (ATM), showing increased genomic instability. Here we show that DNA do uble-stranded break (DSB) repair pathways are involved in the regulation of rAAV transduction efficiency. By quantitative chromatin immunoprecipitatio n, we found that Ku86 and Rad52 proteins associate with viral DNA inside tr ansduced cells. Both proteins are known to competitively recognize hairpin structures and DNA termini and to promote repair of DSBs, the former by fac ilitating nonhomologous end joining and the latter by initiating homologous recombination. We found that rAAV transduction is increased in Ku86-defect ive cells while it is inhibited in Rad52 knockout cells. These results sugg est that binding of Rad52 to the rAAV genome might be involved in processin g of the vector genome through a homologous recombination pathway.